Systems and methods for extending the life of an implanted pulse generator battery

ABSTRACT

Systems and methods for extending the life of an implanted pulse generator battery are disclosed. A representative method for establishing charge parameters for a battery-powered implantable medical device includes receiving a patient-specific therapy signal parameter and, based at least in part on the patient-specific therapy signal parameter, determining a discharge rate for a battery of the implanted medical device. The method can further include determining a therapy run time, based at least in part on the discharge rate. The method can still further include determining at least one battery charging parameter, based at least in part on the run time.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional Application62/067,408, filed on Oct. 22, 2014 and incorporated herein by reference.

TECHNICAL FIELD

The present technology is directed generally to systems and methods forextending the life of an implanted pulse generator battery. Particularembodiments include using patient-specific and/or battery-specificcharacteristics to tailor the parameters in accordance with which thebattery of an implantable impulse generator is charged and/ordischarged.

BACKGROUND

Neurological stimulators have been developed to treat pain, movementdisorders, functional disorders, spasticity, cancer, cardiac disorders,and various other medical conditions. Implantable neurologicalstimulation systems generally have an implantable signal generator andone or more leads that deliver electrical pulses to neurological tissueor muscle tissue. For example, several neurological stimulation systemsfor spinal cord stimulation (SCS) have cylindrical leads that include alead body with a circular cross-sectional shape and one or moreconductive rings (i.e., contacts) spaced apart from each other at thedistal end of the lead body. The conductive rings operate as individualelectrodes and, in many cases, the SCS leads are implantedpercutaneously through a needle inserted into the epidural space, withor without the assistance of a stylet.

Once implanted, the signal generator applies electrical pulses to theelectrodes, which in turn modify the function of the patient's nervoussystem, such as by altering the patient's responsiveness to sensorystimuli and/or altering the patient's motor-circuit output. In SCStherapy for the treatment of pain, the signal generator applieselectrical pulses to the spinal cord via the electrodes. In conventionalSCS therapy, electrical pulses are used to generate sensations (known asparesthesia) that mask or otherwise alter the patient's sensation ofpain. For example, in many cases, patients report paresthesia as atingling sensation that is perceived as less uncomfortable than theunderlying pain sensation.

Conventional implanted SCS pulse generators are typically charged usinga set of fixed charging parameters. FIG. 1 illustrates a representativeprocess 10 in accordance with the prior art for establishing and usingbattery charging parameters for standard implantable pulse generators.The process includes a pre-charge parameter selection process 11 and acharging process 12. The pre-charge parameter selection process 11includes establishing fixed thresholds for charging parameters,including thresholds for charging voltage levels and/or charging currentlevels, and time limits for one or more phases of the charging process12 (block 14). The charging process 12 itself includes an initial periodduring which the battery is charged at a constant current (block 15). Atblock 16, the process includes determining whether an end-of-chargevoltage threshold has been reached. If the voltage threshold has notbeen reached, then the battery is further charged using the constantcurrent value. If the voltage threshold has been reached, then in block17, the battery is further charged at a constant voltage level, ratherthan a constant current level. In block 18, the charger determineswhether a minimum end-of-charge current threshold has been reached or,alternatively, whether a charging time limit has been reached. If eithercondition is met, the charging process stops (block 19). If the relevantcondition is not met, the constant voltage phase of the charging processcontinues until the current threshold or time limit has been reached.

In contrast to traditional or conventional (i.e., paresthesia-based)SCS, a form of paresthesia-free SCS has been developed that uses therapysignal parameters that treat the patient's sensation of pain withoutgenerating paresthesia or otherwise using paresthesia to mask thepatient's sensation of pain. One of several advantages ofparesthesia-free SCS therapy systems is that they eliminate the need foruncomfortable paresthesias, which many patients find objectionable.However, a challenge with paresthesia-free SCS therapy systems is thatthe signal may be delivered at frequencies, amplitudes, and/or pulsewidths that use more power than conventional SCS systems. As a result,the battery of the implanted system can discharge and become depleted atan accelerated rate. Accordingly, a follow-on challenge with providingnon-paresthesia-generating spinal cord stimulation via an implantedpulse generator is that, in at least some cases, it may be difficult tomaintain an effective signal as the charge available from the pulsegenerator battery decreases. One approach to power consumptionchallenges in the context of conventional SCS systems is to increase thefrequency with which the pulse generator is charged, but this can beinconvenient for the patient. Another approach is to add signalconditioning hardware, for example, to boost the voltage provided by thebattery as the battery discharges. A drawback with this approach is thatit can be inefficient. Accordingly, there remains a need for effectiveand efficient therapy signal delivery, despite the possibility ofincreased power consumption resulting from the signal deliveryparameters used for paresthesia-free patient therapy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of a representative charging process inaccordance with the prior art.

FIG. 2A is a partially schematic illustration of an implantable spinalcord modulation system positioned at the spine to deliver therapeuticsignals in accordance with several embodiments in the presenttechnology.

FIG. 2B is a partially schematic, cross-sectional illustration of apatient's spine, illustrating representative locations for implantedlead bodies in accordance with embodiments of the present technology.

FIG. 3 is a flow diagram illustrating a representative process forestablishing and using battery charge parameters in accordance with anembodiment of the present technology.

FIG. 4 is a flow diagram illustrating a representative process forestablishing charging parameters in accordance with another embodimentof the present technology.

FIG. 5 is a flow diagram illustrating a process for establishingpatient-specific charging and/or discharging parameters in accordancewith still another embodiment of the present technology.

FIG. 6 is a flow diagram illustrating a process for placing a battery ina storage stage in accordance with yet another embodiment of the presenttechnology.

DETAILED DESCRIPTION

The present technology is directed generally to systems and methods forextending the life of an implanted pulse generator battery, which isused to deliver electrical signals (also referred to herein as “therapysignals”) to provide patient treatment via spinal cord stimulation (SCS)or other techniques. For example, in one embodiment, the presenttechnology includes establishing charge parameters for the battery ofthe pulse generator (or other implantable medical device) usingpatient-specific therapy signal parameters to establish a discharge ratefor the battery, a therapy run time for the battery, and/or one or moreassociated battery charging parameters. Accordingly, the technology cantailor the battery charging parameters based on a particular patient'stherapy parameters. In further embodiments, the technique can alsoinclude accounting for patient-specific charging habits and/orbattery-specific parameters (e.g., the age of the battery and/or thenumber of times the battery has previously been charged). In any ofthese embodiments, the foregoing techniques can increase the life of thebattery in a manner that is tailored to the specific manner in which thebattery is used. In still further embodiments, methods in accordancewith the present technology can be used to charge or discharge thebattery in preparation for an extended period of storage. Thesetechniques can increase the shelf life of the battery.

General aspects of the environments in which the disclosed technologyoperates are described below under Heading 1.0 (“Overview”) withreference to FIGS. 2A and 2B. Particular embodiments of the technologyare described further under Heading 2.0 (“Representative Embodiments”)with reference to FIGS. 3-6. Additional embodiments are described underHeading 3.0 (“Additional Embodiments”). While the present technology isdescribed in the environment of SCS, one with skill in the art wouldrecognize that one or more aspects of the present technology areapplicable to other, non-SCS implantable devices; e.g., more generally,implantable neurostimulators for treatment of one or more patientindications.

1.0 Overview

One example of a paresthesia-free SCS therapy system is a “highfrequency” SCS system. High frequency SCS systems can inhibit, reduce,and/or eliminate pain via waveforms with high frequency elements orcomponents (e.g., portions having high fundamental frequencies),generally with reduced or eliminated side effects. Such side effects caninclude unwanted paresthesia, unwanted motor stimulation or blocking,unwanted pain or discomfort, and/or interference with sensory functionsother than the targeted pain. In a representative embodiment, a patientmay receive high frequency therapeutic signals with at least a portionof the therapy signal at a frequency of from about 1.5 kHz to about 100kHz, or from about 1.5 kHz to about 50 kHz, or from about 3 kHz to about20 kHz, or from about 5 kHz to about 15 kHz, or at frequencies of about8 kHz, 9 kHz, or 10 kHz. These frequencies are significantly higher thanthe frequencies associated with conventional “low frequency” SCS, whichare generally below 1,200 Hz, and more commonly below 100 Hz.Accordingly, modulation at these and other representative frequencies(e.g., from about 1.5 kHz to about 100 kHz) is occasionally referred toherein as “high frequency stimulation,” “high frequency SCS,” and/or“high frequency modulation.” Further examples of paresthesia-free SCSsystems are described in U.S. Patent Publication Nos. 2009/0204173 and2010/0274314, the respective disclosures of which are hereinincorporated by reference in their entireties.

FIG. 2A schematically illustrates a representative patient therapysystem 200 for providing relief from chronic pain and/or otherconditions, arranged relative to the general anatomy of a patient'sspinal column 291. The system 200 can include a signal generator 201(e.g., an implanted or implantable pulse generator or IPG), which may beimplanted subcutaneously within a patient 290 and coupled to one or moresignal delivery elements or devices 210. The signal delivery elements ordevices 210 may be implanted within the patient 290, typically at ornear the patient's spinal cord midline 289. The signal delivery elements210 carry features for delivering therapy to the patient 290 afterimplantation. The signal generator 201 can be connected directly to thesignal delivery devices 210, or it can be coupled to the signal deliverydevices 210 via a signal link or lead extension 202. In a furtherrepresentative embodiment, the signal delivery devices 210 can includeone or more elongated lead(s) or lead body or bodies 211 (identifiedindividually as a first lead 211 a and a second lead 211 b). As usedherein, the terms signal delivery device, lead, and/or lead body includeany of a number of suitable substrates and/or support members that carryelectrodes/devices for providing therapy signals to the patient 290. Forexample, the lead or leads 211 can include one or more electrodes orelectrical contacts that direct electrical signals into the patient'stissue, e.g., to provide for therapeutic relief. In other embodiments,the signal delivery elements 210 can include structures other than alead body (e.g., a paddle) that also direct electrical signals and/orother types of signals to the patient 290.

In a representative embodiment, one signal delivery device may beimplanted on one side of the spinal cord midline 289, and a secondsignal delivery device may be implanted on the other side of the spinalcord midline 289. For example, the first and second leads 211 a, 211 bshown in FIG. 2A may be positioned just off the spinal cord midline 289(e.g., about 1 mm offset) in opposing lateral directions so that the twoleads 211 a, 211 b are spaced apart from each other by about 2 mm. Inparticular embodiments, the leads 211 may be implanted at a vertebrallevel ranging from, for example, about T8 to about T12. In otherembodiments, one or more signal delivery devices can be implanted atother vertebral levels, e.g., as disclosed in U.S. Patent ApplicationPublication No. 2013/0066411, which is incorporated herein by referencein its entirety.

The signal generator 201 can transmit signals (e.g., electrical signals)to the signal delivery elements 210 that up-regulate (e.g., excite)and/or down-regulate (e.g., block or suppress) target nerves. As usedherein, and unless otherwise noted, the terms “modulate,” “modulation,”“stimulate,” and “stimulation” refer generally to signals that haveeither type of the foregoing effects on the target nerves. The signalgenerator 201 can include a machine-readable (e.g., computer-readable)or controller-readable medium containing instructions for generating andtransmitting suitable therapy signals. The signal generator 201 and/orother elements of the system 200 can include one or more processor(s)207, memory unit(s) 208, and/or input/output device(s) 212. Accordingly,the process of providing modulation signals, providing guidanceinformation for positioning the signal delivery devices 210,establishing battery charging and/or discharging parameters, and/orexecuting other associated functions can be performed bycomputer-executable instructions contained by, on or incomputer-readable media located at the pulse generator 201 and/or othersystem components. Further, the pulse generator 201 and/or other systemcomponents may include dedicated hardware, firmware, and/or software forexecuting computer-executable instructions that, when executed, performany one or more methods, processes, and/or sub-processes describedherein; e.g., the methods, processes, and/or sub-processes describedwith reference to FIGS. 3-6 below. The dedicated hardware, firmware,and/or software also serve as “means for” performing the methods,processes, and/or sub-processes described herein. The signal generator201 can also include multiple portions, elements, and/or subsystems(e.g., for directing signals in accordance with multiple signal deliveryparameters), carried in a single housing, as shown in FIG. 2A, or inmultiple housings.

The signal generator 201 can also receive and respond to an input signalreceived from one or more sources. The input signals can direct orinfluence the manner in which the therapy, charging, and/or processinstructions are selected, executed, updated, and/or otherwiseperformed. The input signals can be received from one or more sensors(e.g., an input device 212 shown schematically in FIG. 2A for purposesof illustration) that are carried by the signal generator 201 and/ordistributed outside the signal generator 201 (e.g., at other patientlocations) while still communicating with the signal generator 201. Thesensors and/or other input devices 212 can provide inputs that depend onor reflect patient state (e.g., patient position, patient posture,and/or patient activity level), and/or inputs that arepatient-independent (e.g., time). Still further details are included inU.S. Pat. No. 8,355,797, incorporated herein by reference in itsentirety.

In some embodiments, the signal generator 201 and/or signal deliverydevices 210 can obtain power to generate the therapy signals from anexternal power source 203. In one embodiment, for example, the externalpower source 203 can by-pass an implanted signal generator and generatea therapy signal directly at the signal delivery devices 210 (or viasignal relay components). The external power source 203 can transmitpower to the implanted signal generator 201 and/or directly to thesignal delivery devices 210 using electromagnetic induction (e.g., RFsignals). For example, the external power source 203 can include anexternal coil 204 that communicates with a corresponding internal coil(not shown) within the implantable signal generator 201, signal deliverydevices 210, and/or a power relay component (not shown). The externalpower source 203 can be portable for ease of use.

In another embodiment, the signal generator 201 can obtain the power togenerate therapy signals from an internal power source, in addition toor in lieu of the external power source 203. For example, the implantedsignal generator 201 can include a non-rechargeable battery or arechargeable battery to provide such power. When the internal powersource includes a rechargeable battery, the external power source 203can be used to recharge the battery. The external power source 203 canin turn be recharged from a suitable power source (e.g., conventionalwall power).

During at least some procedures, an external stimulator or trialmodulator 205 can be coupled to the signal delivery elements 210 duringan initial procedure, prior to implanting the signal generator 201. Forexample, a practitioner (e.g., a physician and/or a companyrepresentative) can use the trial modulator 205 to vary the modulationparameters provided to the signal delivery elements 210 in real time,and select optimal or particularly efficacious parameters. Theseparameters can include the location from which the electrical signalsare emitted, as well as the characteristics of the electrical signalsprovided to the signal delivery devices 210. In some embodiments, inputis collected via the external stimulator or trial modulator and can beused by the clinician to help determine what parameters to vary. In atypical process, the practitioner uses a cable assembly 220 totemporarily connect the trial modulator 205 to the signal deliverydevice 210. The practitioner can test the efficacy of the signaldelivery devices 210 in an initial position. The practitioner can thendisconnect the cable assembly 220 (e.g., at a connector 222), repositionthe signal delivery devices 210, and reapply the electrical signals.This process can be performed iteratively until the practitioner obtainsthe desired position for the signal delivery devices 210. Optionally,the practitioner may move the partially implanted signal deliverydevices 210 without disconnecting the cable assembly 220. Furthermore,in some embodiments, the iterative process of repositioning the signaldelivery devices 210 and/or varying the therapy parameters may not beperformed.

The signal generator 201, the lead extension 202, the trial modulator205 and/or the connector 222 can each include a receiving element 209.Accordingly, the receiving elements 209 can be patient implantableelements, or the receiving elements 209 can be integral with an externalpatient treatment element, device or component (e.g., the trialmodulator 205 and/or the connector 222). The receiving elements 209 canbe configured to facilitate a simple coupling and decoupling procedurebetween the signal delivery devices 210, the lead extension 202, thepulse generator 201, the trial modulator 205 and/or the connector 222.The receiving elements 209 can be at least generally similar instructure and function to those described in U.S. Patent ApplicationPublication No. 2011/0071593, incorporated by reference herein in itsentirety.

After the signal delivery elements 210 are implanted, the patient 290can receive therapy via signals generated by the trial modulator 205,generally for a limited period of time. During this time, the patientwears the cable assembly 220 and the trial modulator 205 outside thebody. Assuming the trial therapy is effective or shows the promise ofbeing effective, the practitioner then replaces the trial modulator 205with the implanted signal generator 201, and programs the signalgenerator 201 with therapy programs selected based on the experiencegained during the trial period. Optionally, the practitioner can alsoreplace the signal delivery elements 210. Once the implantable signalgenerator 201 has been positioned within the patient 290, the therapyprograms provided by the signal generator 201 can still be updatedremotely via a wireless physician's programmer (e.g., a physician'slaptop, a physician's remote or remote device, etc.) 217 and/or awireless patient programmer 206 (e.g., a patient's laptop, patient'sremote or remote device, etc.). Generally, the patient 290 has controlover fewer parameters than does the practitioner. For example, thecapability of the patient programmer 206 may be limited to startingand/or stopping the signal generator 201, and/or adjusting the signalamplitude. The patient programmer 206 may be configured to accept painrelief input as well as other variables, such as medication use.

In any of the foregoing embodiments, the parameters in accordance withwhich the signal generator 201 provides signals can be adjusted duringportions of the therapy regimen. For example, the frequency, amplitude,pulse width, and/or signal delivery location can be adjusted inaccordance with a pre-set therapy program, patient and/or physicianinputs, and/or in a random or pseudorandom manner. Such parametervariations can be used to address a number of potential clinicalsituations. Certain aspects of the foregoing systems and methods may besimplified or eliminated in particular embodiments of the presentdisclosure. Further aspects of these and other expected beneficialresults are detailed in U.S. Patent Application Publication Nos.2010/0274314; 2009/0204173; and 2013/0066411 (all previouslyincorporated by reference) and U.S. Patent Application Publication No.2010/0274317, which is incorporated herein by reference in its entirety.

FIG. 2B is a cross-sectional illustration of the spinal cord 291 and anadjacent vertebra 295 (based generally on information from Crossman andNeary, “Neuroanatomy,” 1995 (published by Churchill Livingstone)), alongwith multiple leads 211 (shown as leads 211 a-211 e) implanted atrepresentative locations. For purposes of illustration, multiple leads211 are shown in FIG. 2B implanted in a single patient. In actual use,any given patient will likely receive fewer than all the leads 211 shownin FIG. 2B.

The spinal cord 291 is situated within a vertebral foramen 288, betweena ventrally located ventral body 296 and a dorsally located transverseprocess 298 and spinous process 297. Arrows V and D identify the ventraland dorsal directions, respectively. The spinal cord 291 itself islocated within the dura mater 299, which also surrounds portions of thenerves exiting the spinal cord 291, including the ventral roots 292,dorsal roots 293 and dorsal root ganglia 294. The dorsal roots 293 enterthe spinal cord 291 at the dorsal root entry zone 287, and communicatewith dorsal horn neurons located at the dorsal horn 286. In oneembodiment, the first and second leads 211 a, 211 b are positioned justoff the spinal cord midline 289 (e.g., about 1 mm. offset) in opposinglateral directions so that the two leads 211 a, 211 b are spaced apartfrom each other by about 2 mm, as discussed above. In other embodiments,a lead or pairs of leads can be positioned at other locations, e.g.,toward the outer edge of the dorsal root entry zone 287 as shown by athird lead 211 c, or at the dorsal root ganglia 294, as shown by afourth lead 211 d, or approximately at the spinal cord midline 289, asshown by a fifth lead 211 e.

2.0 Representative Embodiments

Systems of the type described above with reference to FIGS. 2A-2B caninclude implanted pulse generators (IPGs) having rechargeable batteriesor other rechargeable power sources that are periodically recharged withan external charger. Over the course of a given therapeutic regimen, thepatient and/or the practitioner may change the parameters in accordancewith which the electrical signals are delivered to the patient. As theparameters change, the rate at which electrical current is drawn ordrained from the battery can also change. In addition, differentpatients may charge their batteries in accordance with differentschedules, and/or may vary in the consistency with which they adhere tosuch schedules. Still further, the characteristics of the rechargeablebattery can change over the course of time. For example, the overallcharge capacity of the battery will typically decrease over time, e.g.,due to chemical degradation. Techniques in accordance with the presenttechnology, described further below, can tailor the manner in which thebattery is charged and/or discharged by taking into account one or moreof the foregoing variables to increase the usable life of the battery.

FIG. 3 is a flow diagram illustrating an overall process 300 configuredin accordance with an embodiment of the present technology. Block 301includes setting, reestablishing, identifying and/or obtaining initialand/or default therapy signal parameters. The therapy signal parameterscan include the frequency, pulse width, inter-pulse interval, amplitude,duty cycle and/or any other suitable parameters of the therapy signalthat may affect the rate at which the signal uses energy or chargeprovided by the battery of the implantable medical device as the signalis applied to the patient. In block 302, the rate at which the batteryis discharged is calculated, estimated, or otherwise determined based atleast in part on one or more of the therapy parameters identified inblock 301. As used herein, the phrase “based at least in part” refers toa determination that is based on the identified parameter(s), with orwithout being based on an additional factor or factors. In block 303,the run-time for the IPG (based on a single charge) is determined, basedat least in part on the discharge rate calculated at block 302.Accordingly, high discharge rates will produce shorter run-times and lowdischarge rates will produce longer run-times. At block 304, the process300 includes setting, establishing, identifying or otherwise determiningsuitable battery charge parameters, based at least in part on thedischarge rate and/or the run-time determined at blocks 302 and 303,respectively. As will be described in further detail below, the chargeparameters can include the points at which various phases of thecharging process are completed. Once the charge parameters areestablished, the parameters can be used to charge the battery (block305). The parameters can be changed in response to changes in thetherapy parameters, and/or can be checked and changed on a periodic,pre-established basis (block 306).

FIG. 4 is a flow diagram illustrating a representative process 400, withadditional details provided for several of the process steps describedabove with reference to FIG. 3. For example, the process 400 can includecollecting patient-specific data (block 401). As used herein, the term“patient-specific data” refers generally to data that varies from onepatient to another. The term does not require that the data be uniquefor each patient. In a particular embodiment, the patient-specific datacan be collected at the IPG itself. Accordingly, the IPG can includefeatures for obtaining and at least temporarily storing patient-specificdata. An advantage of collecting the patient-specific data at the IPG isthat much, if not all, of the data may already be collected by and/orstored at the IPG during normal operations and accordingly, collectingthe data is not expected to burden either the storage capacity or thememory capacity of the IPG. In another aspect of this embodiment, thesteps for processing the data (in addition to collecting the data) canalso be carried out at the IPG. An advantage of this feature is that thedata can readily be transmitted to a battery charger during a rechargeoperation, without requiring an additional device.

The process of collecting patient-specific data can include receivingpatient-specific therapy signal data (block 402), receiving at least onepatient-specific charging characteristic (block 403) and/or receiving atleast one battery-specific battery characteristic (block 404). Thepatient-specific therapy signal data (block 402) can include the signaldelivery parameters in accordance with which the IPG generates anddelivers electrical therapy signals to the patient. The discharge ratecan be calculated or otherwise determined, based at least in part on theforegoing patient-specific therapy signal data (block 405). For example,the frequency, pulse width, inter-pulse interval, amplitude, and/or dutycycle of the signal can be used to determine the rate at which charge isdrawn from the battery. These foregoing signal delivery parameters aretypically stored at the IPG (to be used by the IPG for generating thetherapy signal) and are provided to the IPG via a physician and/or thepatient.

The patient-specific therapy signal data can include other parameters,in addition to or in lieu of the foregoing signal delivery parameters.Such parameters can include impedances, e.g., impedances of one or morecomponents or circuits used to deliver the electrical therapy signal tothe patient. For example, a representative impedance value is theimpedance of the electrical contacts (e.g., a bipolar pair of contacts),intervening patient tissue, and electrical wires in the lead or othersignal delivery device.

The patient-specific charging characteristic (block 403) and thebattery-specific battery characteristic (block 404) can be used alone ortogether to calculate the charge and/or discharge limits (block 406),e.g., in combination with the discharge rate determined at block 405.For example, the patient-specific charging characteristic can includehistorical data identifying how often the patient typically charges thebattery and/or the consistency with which the patient adheres to acharging schedule. The battery-specific battery characteristic caninclude the age of the battery and/or the number of charging/dischargingcycles undergone by the battery. For example, as a battery ages, theoverall charge capacity of the battery typically decreases. As thenumber of charge/discharge cycles of the battery increases, the chargecapacity of the battery also typically decreases. One or both of thesefactors can be considered in determining the charge and/or dischargelimits in block 406.

At block 407, the process can include determining if the inputsdescribed above (e.g., with reference to block 402, block 403, and/orblock 404) have changed. If the inputs have changed, then new inputs arereceived at blocks 402, 403 and 404, respectively, and the dischargerate and charge/discharge limits are re-determined. Alternatively, theprocess can include re-determining the discharge rates andcharge/discharge limits if a (pre-established) period of time haselapsed. For example, if the discharge rates and charge/discharge limitshave not been re-determined for a period of several days, weeks ormonths, the process can automatically re-determined these quantities toensure that they are up to date. Once it has been determined that thequantities are current, then the charge/discharge limits are set (ormaintained) in block 408. These parameters are then used to charge thebattery of the implantable pulse generator (block 409).

FIG. 5 illustrates a process 500 in accordance with still a furtherembodiment of the present technology, illustrating further details andspecific parameters in accordance with which the determinationsdescribed above with reference to FIGS. 3 and 4 may be carried out.Block 501 includes receiving or retrieving patient-specific therapysignal data, which in turn can include receiving or retrievingpatient-specific therapy signal settings (block 502) and/or receiving orretrieving historical patient-specific therapy signal data (block 503).The patient-specific therapy signal settings, as discussed above, caninclude amplitude, frequency, pulse width, inter-pulse interval and/orduty cycle. Other patient-specific variables associated with deliveringthe therapy include therapy signal circuit impedances. Depending uponthe embodiment, at least some of the foregoing parameters may beselectable by the patient, by the practitioner, and/or by themanufacturer. For example, in a representative embodiment, the patienthas control over the amplitude at which the therapy signal is delivered,within ranges set by the practitioner. The practitioner has control overthe duty cycle and, in particular embodiments, the frequency, pulsewidth, and/or inter-pulse interval. In still further embodiments, thepractitioner may have control over fewer of the foregoing parameters,with the remaining parameters being established by the manufacturerand/or being calculated based upon manufacturer presets in combinationwith the practitioner-selected parameters. For example, the inter-pulseinterval can be calculated based upon the signal frequency and pulsewidth, and the frequency and/or pulse width can be set by themanufacturer or by the practitioner. In a typical process, theparameters set by the practitioner, and any parameters calculated orotherwise determined from such parameters, are established by thephysician's programmer 217 (FIG. 2A) and transmitted wirelessly to theIPG.

In any of the foregoing embodiments, the patient-specific therapy signalsettings can be sufficient to determine the discharge rate (block 505)alone, or in combination with the historical patient-specific therapysignal data identified at block 503. The historical data can include theon/off times historically selected by the patient at one or morepatient-specific therapy signal settings. The on/off times can differfrom the duty cycle (described above with reference to block 502) inthat they may be selected by the patient, while the duty cycle may beselected by the practitioner. For example, the on/off time can includetime periods when the patient turns the IPG-generated signal off, e.g.,when particular activities engaged in by the patient are not benefitedfrom receiving the signal. Unlike the duty cycle, which is typicallyrepeated on a very regular schedule (e.g., with stimulation on forseveral seconds and off for several minutes), the on/off time may varyfrom day to day depending upon the activities engaged in by the patient.

At block 505, the process includes determining the discharge rate. Asdiscussed above, this process can include determining the discharge ratebased on the amplitude, frequency, pulse width, duty cycle, and/oron/off times by determining the energy associated with a signal havingthe signal characteristics described by the foregoing features. Thedischarge rate can take into account impedance values that may vary frompatient to patient.

At block 506, the process includes receiving or retrievingpatient-specific charging characteristics. Representative chargingcharacteristics include a frequency with which the patient hashistorically charged the battery, a duration for which the patientcharges the battery when the battery is charged, and/or a consistencywith which the patient charges the battery. In particular embodiments,block 506 can include receiving a patient-specific chargingcharacteristic that includes a charging interval value based at least inpart on multiple prior intervals between charging events for thebattery.

At block 507, the process includes receiving or retrievingbattery-specific battery characteristics. The battery characteristicscan include the age of the battery, the number of charge cyclesundergone by the battery, the total amount of charge delivered by thebattery (e.g., over many charge cycles), and/or other aspects of thebattery that may vary from one patient's IPG to another patient's IPG.For example, an older battery and/or a battery that has been charged anddischarged many times will typically have a lower total charge capacitythan a battery that is new and/or has undergone fewer charge/dischargecycles. The data corresponding to these characteristics can be stored atthe IPG and updated periodically. For example, the IPG can store themanufacture date of the battery. Each time the battery is charged, theIPG can increment a battery charge counter. At block 508, the run timefor battery is determined, based at least in part on at least onecharging characteristic, battery characteristic, or othercharacteristics. Representative characteristics include battery capacityand/or discharge rate.

The foregoing characteristics can be used to determine a margin by whichto adjust the overall run time for the battery (block 509). In general,the margin is selected to protect the patient from inadvertentlydischarging the battery below a level at which the implantable devicecan support delivering the therapy signal. For example, if the patientcharges the battery frequently (or has a short charging interval betweencharges), the margin can be relatively small because the likelihood thatthe patient will fully discharge the battery is reduced. Conversely, ifthe patient charges the battery infrequently, the margin can be larger.

The margin determination can be based at least in part on theconsistency with which the patient charges the battery (in addition toor in lieu of considering the frequency with which the patient charges),based on historical information collected at the IPG. For example, ifthe patient tends to charge frequently but is inconsistent andaccordingly has a significant number of large intervals betweencharging, then the margin applied to the discharge rate can beincreased. If the patient is consistent in his or her charging habits(e.g., reliably charging the battery every day or reliably charging thebattery every week) then the margin can be decreased.

The margin determination can include the consistency of the chargeperiod, in addition to or in lieu of the foregoing characteristics. Forexample, if the patient reliably charges the battery for a consistentperiod of time, the margin can be decreased. If instead, the patientsometimes charges the battery for a few minutes and other times forsignificantly longer periods of time, then the margin can be increased.In the illustrated embodiment, the margin is added to the run time. Inother embodiments, a margin can be applied to other factors used todetermine the battery charging/discharging parameters, e.g., the margincan be applied to the discharge rate.

At block 510, the process includes setting end-of-charge (EOC) limits.Block 511 identifies representative factors that are considered incalculating the overall EOC limits. Such factors include the desirablefeature of targeting the middle range of the charge capacity of thebattery. For example, rather than charging the battery to 100%, arepresentative charge limit can be set to be 70%, 80%, or 90% of thefull capacity of the battery. In addition to or in lieu of the foregoingconsideration, the EOC limit for the complete charge limit of thebattery can be adjusted depending on factors including the age of thebattery. In a particular embodiment, the overall charge limits areadjusted upwardly toward the end of the life of the battery. Forexample, toward the end of the life of the battery, the benefit ofcharging the battery to less than its full capacity may be outweighed bythe benefit of utilizing the final remaining charge capacity of thebattery, which can be accomplished by charging the battery to (or closeto) its full capacity.

The foregoing EOC limits refer to the complete or overall charge of thebattery. In block 512, intermediate charge parameters can also bedetermined as part of the overall process of setting the EOC limits. Forexample, when the battery is charged using a primarily constant currentprocess, one EOC limit is the EOC voltage threshold. The EOC voltagethreshold corresponds to the voltage at which the constant currentprocess ceases and the remaining charge is carried out using a differentprocess, e.g., a constant voltage process. Other representative EOClimits include an EOC current threshold, which can correspond to theminimum current (after the EOC voltage threshold has been surpassed) atwhich the battery is to continue charging. Once this limit has beenreached, the battery is considered fully charged and the overallcharging process is complete. Alternatively, the EOC current thresholdcan be replaced with a time limit. The time limit can correspond to themaximum charge time after the EOC voltage threshold has been surpassed.In other embodiments, the foregoing limits can be re-ordered and/orreplaced with other suitable limits, e.g., if the battery is chargedusing a primarily constant voltage process.

In still further embodiments, the process can include setting anend-of-discharge (EOD) limit at block 513, in addition to or in lieu ofsetting EOC limits. For example, if the patient charges infrequentlyand/or has an inconsistent charging history, then the end-of-dischargelimit can be set conservatively so as not to approach the end of thebattery's capacity too closely. In any of these embodiments, the EODlimit can correspond to a point at which a notification is issued to thepatient, and/or a point in time when a low battery or power savings modeis entered. In a low battery mode, certain functions of the IPG can besuspended to allow the therapy to continue being delivered until thepatient is able to charge the batteries. For example, in a particularembodiment, the IPG can suspend all functions (e.g., signal deliveryfunctions and telemetry functions) except a clock function. In a furtheraspect of this embodiment, the IPG automatically resumes the therapyprogram it was delivering in response to being recharged. This is unlikeconventional systems that require the patient to manually turn the IPGon and/or manually re-start a therapy program after the IPG is rechargedfrom a low battery or power savings mode or state.

One feature of at least of at least some of the foregoing embodiments isthat the charging parameters for the battery of an implantable pulsegenerator can be tailored, adjusted, determined, calculated, set, orotherwise established in a manner that reflects patient-specific and/orbattery-specific characteristics. An advantage of this arrangement isthat it can extend the life of the battery and thereby reduce or eveneliminate the need to replace the battery.

Another feature of at least some of the foregoing embodiments is thatthe processes for establishing and/or adjusting the charge and/ordischarge parameters can be automated. An advantage of this feature isthat it can reduce or eliminate any effort on the part of the patientand/or the practitioner and/or the company representative to achieve thebenefits of tailored charge/discharge parameters. Still anotheradvantage of the foregoing features is that, in particular embodiments,the patients perception of the consistency of the system can beimproved. For example, by automatically providing and adjusting (asneeded) the margins within which the IPG battery operates, the patientwill be less likely to over-discharge the battery.

FIG. 6 is a flow diagram illustrating a process for placing the batteryof an implantable medical device in a storage state or stock mode, inaccordance with a particular embodiment of the present technology. Thistechnique can be used by the manufacturer to place the battery in astorage state prior to releasing the product for sale and/ordistribution. In another embodiment, the process can be used by apractitioner (e.g., a representative of the manufacturer) to re-store abattery. For example, the battery may be re-stored if it has been takenout of storage and needs to be placed back into storage, or if thebattery has exceeded its initial storage period and is to be placed backin storage. Typically, the battery is installed in the IPG at the timethe storage state is entered, so both the IPG and the battery enter thestorage state together.

The process 600 can include receiving an indication corresponding to anupcoming charging event that includes placing the battery in a storagestate (block 601). For example, the indication can include a request bya manufacturer or practitioner to have the battery placed in a storagestate. At block 602, the process includes determining if a charge stateof the battery is within a target charge range. The target charge rangeis typically less than fully charged, but more than completelydischarged. It is typically advantageous to store the battery with lessthan a full charge because storing a fully charged battery can increasethe likelihood and/or extent to which the battery capacity fades.

At block 603, the process includes determining if the charge state ofthe battery is above the charge range. If so, then in block 604, theprocess can include automatically providing an indication to thateffect, and/or automatically discharging the battery at least until thebattery is at or within the charge range. The indication can include agraphical indication (at a graphical user interface) to an operatordirecting the operator to discharge the battery, and in otherembodiments can include other types of indications.

If the charge state is below the charge range, then in block 605, theprocess can include automatically providing an indication to thateffect, and/or automatically charging the battery at least until thebattery is at or within the charge range. In block 606, the processincludes optionally providing an indication when the battery is at orwithin the target charge range. At this point, the operator can storethe battery and/or the IPG in which the battery is placed.

In other embodiments, the process 600 can include other inputs and/orprocesses. For example, the process 600 can include receiving an inputcorresponding to an amount of time the battery is to be stored. Based onthis input, the process can include adjusting the target charge range.For example, if the battery is to be stored for a longer period of time,the process can charge the battery to a higher charge state. If thebattery is to be stored for a relatively short period of time, the upperend of the charge range can be reduced. In any of these embodiments, anadvantage of the foregoing features is that the features facilitate (andin at least some embodiments, automate) more precise charging for thebattery, which can in turn reduce the likelihood that the battery willbe overcharged or undercharged when it is placed in storage.

As part of entering the storage state or stock mode, the foregoingprocess can further include de-powering all the electronics of the IPG.For example, the process can include disabling or de-powering a MOSFETbetween the battery and all electronics of the IPG. In otherembodiments, other elements or arrangements can be used to perform thisfunction. In any of these embodiments, the MOSFET (or other interruptdevice) can be re-powered, reset or otherwise re-configured to activatethe previously de-powered electronics, in response to the presence of acharging coil, currents induced by the charging coil, and/or otheraspect of a charging event.

From the foregoing, it will be appreciated that specific embodiments ofthe presently disclosed technology have been described herein forpurposes of illustration, but that various modifications may be madewithout deviating from the disclosed technology. For example, someembodiments were described above in the context of particular therapysignals that produce pain relief without generating paresthesia. Inother embodiments, other methodologies may be used to provide paintherapy to the patient, and in some instances, such methodologies mayprovide paresthesia-free pain relief.

In particular embodiments, representative current amplitudes for thetherapy signal are from 0.1 mA to 20 mA, or 0.5 mA to 10 mA, or 0.5 mAto 7 mA, or 0.5 mA to 5 mA. Representative pulse widths range from about10 microseconds to about 333 microseconds, about 10 microseconds toabout 166 microseconds, about 20 microseconds to about 100 microseconds,about 30 microseconds to about 100 microseconds, and about 30microseconds to about 40 microseconds. Duty cycles can range from about10% to about 100%, and in a particular duty cycle, signals are deliveredfor 20 seconds and interrupted for 2 minutes (an approximately 14% dutycycle). In other embodiments, these parameters can have other suitablevalues. For example, in at least some embodiments, the foregoing systemsand methods may be applied to therapies that have frequencies outsidethe ranges discussed above (e.g., 1.5 kHz-100 kHz) but which also do notproduce paresthesia. Representative pulse widths (which can be deliveredat frequencies above or below 1.5 kHz, depending upon the embodiment)include pulse widths from 10-50 microseconds, 20-40 microseconds, 25-35microseconds, 30-35 microseconds, and 30 microseconds.

In still further embodiments, techniques generally similar to thosedescribed above may be applied to therapies that are directed to tissuesother than the spinal cord. Representative tissues can includeperipheral nerve tissue and/or brain tissue.

In other embodiments, similar or identical techniques for handlingcharging and/or discharging processes and parameters may be used in thecontext of therapy parameters that generate paresthesia. Certainembodiments were described above in the context of spinal cordstimulators, and in other embodiments, generally similar or identicalcharge parameter selection techniques can be used for implantabledevices that perform functions other than spinal cord stimulation. Inseveral of the embodiments discussed above, retrieving, processingand/or other data functions are performed at the IPG. In otherembodiments, at least some of the foregoing processes can be carried outby another component of the overall system, for example, anon-implantable component. In particular, certain processes can becarried out by a charger, based on data provided by the IPG at the timeof charging.

Many of the foregoing processes include determining values, parameters,ranges and/or other quantities. As used herein, “determining” caninclude calculating, extrapolating, interpolating, applying table lookup functions, estimating, and/or other suitable methods.

Certain aspects of the technology described in the context of particularembodiments may be combined or eliminated in other embodiments. Forexample, in some embodiments, the foregoing techniques can include usingpatient-specific therapy parameters, or battery-specific batteryparameters, or a combination of both. In other embodiments, certainsteps of an overall process can be re-ordered or eliminated. Forexample, blocks 603, 604, and 605 (discussed above with reference toFIG. 6) can be re-ordered so that determining if the charge state isbelow the charge range is performed first.

3.0 Additional Embodiments

In one embodiment, there is provided a method for establishing chargeparameters for a battery-powered implantable medical device, comprising:receiving a patient-specific therapy signal parameter; based at least inpart on the patient-specific therapy signal parameter, determining adischarge rate for a battery of the implantable medical device; based atleast in part on the discharge rate, determining a therapy run time; andbased at least in part on the run time, determining at least one batterycharging parameter. The process of receiving the at least onepatient-specific therapy signal parameter may be performed by theimplantable medical device. The patient-specific therapy signalparameter may include a therapy signal amplitude, a therapy signalpulsewidth, or a therapy signal duty cycle. A representative method mayfurther comprise receiving at least one charging characteristic, withthe at least one charging characteristic including at least one of abattery-specific battery characteristic or a patient-specific chargingcharacteristic; and based at least in part on the at least one chargingcharacteristic and the discharge rate, determining a run time for theimplantable medical device. The patient-specific charging characteristiccan include a patient-specific charging interval, a patient-specificcharging frequency, and/or a patient-specific charging consistency. Thebattery-specific battery characteristic can include an age of thebattery, or a number of charging cycles undergone by the battery. The atleast one charging parameter can include an end of charge limit, whichcan in turn include a voltage limit at which a constant current phase ofa charging process ceases.

In another embodiment, there is provided a method for programming abattery-powered implantable medical device, comprising: programming theimplantable medical device with instructions that, when executed:receive at least one patient-specific therapy signal parameter; direct apatient therapy signal to a signal delivery device in accordance withthe at least one patient-specific therapy signal parameter; based at theleast on the at least one patient-specific therapy signal parameter,determine a discharge rate for a battery of the implantable medicaldevice; based at least in part of the discharge rate, determine atherapy run time; and based at least in part on the run time, determineat least one battery charging parameter.

In another embodiment, there is provided an implantable medical device,comprising: an implantable housing; and a pulse generator carried by thehousing, the pulse generator being programmed with instructions that,when executed: receive at least one patient-specific therapy signalparameter; direct a patient therapy signal to a signal delivery devicein accordance with the at least one patient-specific therapy signalparameter; based at least on the at least one patient-specific therapysignal parameter, determine a discharge rate for a battery of theimplantable medical device; based at least in part on the dischargerate, determine a therapy run time; and based at least in part on therun time, determine at least one battery charging parameter.

In yet another embodiment, there is provided a method for charging abattery of an implantable medical device, comprising receiving anindication corresponding to an upcoming charging event that includesplacing the battery in a storage state; determining if a charge state ofthe battery is within a target charge range; if the charge state isabove the charge range, (a) automatically discharging the battery atleast until the battery is at or within the charge range, or (b)automatically providing an indication that the battery is to bedischarged prior to storage, or both (a) and (b); and if the chargestate is below the charge range, (c), automatically charging the batteryat least until the battery is at or within the charge range or (d)automatically providing an indication that the battery is to be charged,or both (c) and (d).

Implantable medical devices in accordance with still further embodimentscomprise: an implantable housing; and a pulse generator carried by thehousing, the pulse generator being programmed with instructions that,when executed, receive an indication corresponding to an upcomingcharging event that includes placing the battery in a storage state;determine if a charge state of the battery is within a target chargerange; if the charge state is above the charge range, (a) automaticallyprovide an indication that the battery is to be discharged prior tostorage, or (b) automatically discharge the battery at least until thebattery is at or within the charge range, or both (a) and (b); and ifthe charge state is below the charge range, (c) automatically provide anindication that the battery is to be charged, or (d) automaticallycharge the battery at least until the battery is at or within the chargerange, or both (c) and (d).

While advantages associated with certain embodiments of the disclosedtechnology have been described in the context of those embodiments,other embodiments may also exhibit such advantages, and not allembodiments need necessarily exhibit such advantages to fall within thescope of the present technology.

To the extent that any of the foregoing patents, published applications,and/or other materials incorporated herein by reference conflict withpresent disclosure, the present disclosure controls.

I claim:
 1. A method for establishing charge parameters for abattery-powered implantable medical device, comprising: receiving apatient-specific therapy signal parameter; based at least in part on thepatient-specific therapy signal parameter, determining a discharge ratefor a battery of the implantable medical device; based at least in parton the discharge rate, determining a therapy run time; based at least inpart on the therapy run time, determining at least one battery chargingparameter; and charging the battery of the implantable medical deviceusing the determined at least on battery charging parameter.
 2. Themethod of claim 1 wherein the process of receiving the at least onepatient-specific therapy signal parameter is performed by theimplantable medical device.
 3. The method of claim 1 wherein thepatient-specific therapy signal parameter includes a therapy signalamplitude.
 4. The method of claim 1 wherein the patient-specific therapysignal parameter includes a therapy signal pulse width.
 5. The method ofclaim 1 wherein the patient-specific therapy signal parameter includes atherapy signal duty cycle.
 6. The method of claim 1 wherein thepatient-specific therapy signal parameter includes at least one of atherapy on time and a therapy off time.
 7. The method of claim 1 whereinthe patient-specific therapy signal parameter includes an impedance of acircuit or element of a circuit used to deliver therapy to the patient.8. The method of claim 1, further comprising: receiving at least onecharging characteristic, the at least one charging characteristicincluding at least one of a battery-specific battery characteristic or apatient-specific charging characteristic; and wherein determining thetherapy run time includes determining the therapy run time based atleast in part on the at least one charging characteristic.
 9. The methodof claim 8 wherein the patient-specific charging characteristic includesa patient-specific charging interval.
 10. The method of claim 8 whereinthe patient-specific charging characteristic includes a patient-specificcharging frequency.
 11. The method of claim 8 wherein thepatient-specific charging characteristic includes a patient-specificcharging consistency.
 12. The method of claim 8 wherein thebattery-specific battery characteristic includes an age of the battery.13. The method of claim 8 wherein the battery-specific batterycharacteristic includes a number of charging cycles undergone by thebattery.
 14. The method of claim 1 wherein the at least one chargingparameter includes an end-of-charge limit.
 15. The method of claim 14wherein the end-of-charge limit includes a voltage limit at which aconstant current phase of a charging process ceases.
 16. The method ofclaim 1, further comprising, based at least in part on the dischargerate and the therapy run time, determining at least one batterydischarge parameter.
 17. The method of claim 16 wherein the at least onebattery discharge parameter includes a charge capacity limit below whicha low charge indication is directed.
 18. The method of claim 1, whereinthe pulse generator is programmed with instructions that, when executed:receive an indication corresponding to an upcoming charging event thatincludes placing the battery in a storage state; determine if a chargestate of the battery is within a target charge range; if the chargestate is above the target charge range, (a) automatically discharge thebattery at least until the battery is at or within the target chargerange, or (b) automatically provide an indication that the battery is tobe discharged prior to storage, or both (a) and (b); and if the chargestate is below the target charge range, (c) automatically charge thebattery at least until the battery is at or within the target chargerange, or (d) automatically provide an indication that the battery is tobe charged, or both (c) and (d).
 19. The method of claim 18 wherein theindication corresponding to the upcoming charging event includes anindication of a period of time for which the battery is to be stored.20. The method of claim 18, wherein the pulse generator is programmedwith instructions that, when executed, provide an indication that thebattery is at or within the target charge range.
 21. A method forestablishing charge parameters for a battery-powered implantable medicaldevice, comprising: receiving, at the battery-powered implantablemedical device, a patient-specific therapy signal amplitude; based on atherapy signal frequency value, a therapy pulse width and thepatient-specific therapy signal amplitude, determining a discharge ratefor a battery of the implantable medical device; receiving, at thebattery-powered implantable medical device, a battery-specific batterycharacteristic that includes a battery-specific number of prior chargingcycles; receiving, at the battery-powered implantable medical device, apatient-specific charging characteristic that includes a chargingfrequency value; based on the discharge rate, the battery-specificbattery characteristic, and the charging characteristic, determining arun time; based at least in part on the discharge rate and the run time,determining at least one battery charging parameter; and charging thebattery of the implantable medical device using the determined at leastone battery charging parameter.
 22. The method of claim 21 wherein theat least one battery charging parameter includes a voltage limit atwhich a constant current phase of a charging process ceases.
 23. Themethod of claim 21, further comprising recording the multiple priorintervals between charging events for the battery at the implantablepulse generator.
 24. A method for programming a battery-poweredimplantable medical device, comprising: programming the implantablemedical device with instructions that, when executed: receive at leastone patient-specific therapy signal parameter; direct a patient therapysignal to a signal delivery device in accordance with the at least onepatient-specific therapy signal parameter; based at least on the atleast one patient-specific therapy signal parameter, determine adischarge rate for a battery of the implantable medical device; based atleast in part on the discharge rate, determine a therapy run time; basedat least in part on the therapy run time, determine at least one batterycharging parameter; and charge the battery of the implantable medicaldevice using the determined at least one battery charging parameter. 25.The method of claim 24 wherein the patient-specific therapy signalparameter includes a therapy signal amplitude.
 26. The method of claim24 wherein the patient-specific therapy signal parameter includes atherapy signal pulse width.
 27. The method of claim 24 wherein thepatient-specific therapy signal parameter includes a therapy signal dutycycle.
 28. The method of claim 24, further comprising: receiving atleast one charging characteristic, the at least one chargingcharacteristic including at least one of a battery-specific batterycharacteristic or a patient-specific charging characteristic; andwherein determining the therapy run time includes determining thetherapy run time based at least in part on the at least one chargingcharacteristic.
 29. The method of claim 28 wherein the patient-specificcharging characteristic includes a patient-specific charging frequency.30. The method of claim 28 wherein the patient-specific chargingcharacteristic includes a patient-specific charging consistency.
 31. Animplantable medical device, comprising: an implantable housing; and apulse generator carried by the housing, the pulse generator beingprogrammed with instructions that, when executed: receive at least onepatient-specific therapy signal parameter; direct a patient therapysignal to a signal delivery device in accordance with the at least onepatient-specific therapy signal parameter; based at least on the atleast one patient-specific therapy signal parameter, determine adischarge rate for a battery of the implantable medical device; based atleast in part on the discharge rate, determine a therapy run time; basedat least in part on the therapy run time, determine at least one batterycharging parameter; and charge the battery of the implantable medicaldevice using the determined at least one battery charging parameter. 32.The device of claim 31 wherein the patient-specific therapy signalparameter includes a therapy signal amplitude.
 33. The device of claim31 wherein the patient-specific therapy signal parameter includes atherapy signal pulse width.
 34. The device of claim 31 wherein thepatient-specific therapy signal parameter includes a therapy signal dutycycle.
 35. The device of claim 31 wherein the pulse generator isprogrammed with instructions that, when executed: receive at least onecharging characteristic, the at least one charging characteristicincluding at least one of a battery-specific battery characteristic or apatient-specific charging characteristic; and wherein determining thetherapy run time includes determining the therapy run time based atleast in part on the at least one charging characteristic.
 36. Thedevice of claim 35 wherein the patient-specific charging characteristicincludes a patient-specific charging frequency.
 37. The device of claim35 wherein the patient-specific charging characteristic includes apatient-specific charging consistency.
 38. The device of claim 31,wherein the pulse generator is programmed with instructions that, whenexecuted: receive an indication corresponding to an upcoming chargingevent that includes placing the battery in a storage state; determine ifa charge state of the battery is within a target charge range; if thecharge state is above the target charge range, (a) automatically providean indication that the battery is to be discharged prior to storage, or(b) automatically discharge the battery at least until the battery is ator within the target charge range, or both (a) and (b); and if thecharge state is below the charge range, (c) automatically provide anindication that the battery is to be charged, or (d) automaticallycharge the battery at least until the battery is at or within the chargerange, or both (c) and (d).
 39. The system of claim 38 wherein the pulsegenerator includes circuitry configured to generate a therapy signal,and wherein the system further comprises: an interrupt device coupledbetween the circuitry and the battery, the interrupt device beingconfigured to interrupt power from the battery to the circuitry afterthe charge state of the battery is determined, the interrupt devicebeing configured to restore power from the battery to the circuitry inresponse to a charging event.